Material extruder

ABSTRACT

A method and apparatus for extruding viscous materials is provided. A dispenser comprises a control mechanism(s), a material containing structure and ports adapted to be coupled to a portable high-pressure gas source. A user controls a flow of the high-pressure gas with a control mechanism such as a trigger. The gas moves a piston inside the material containing structure and displaces viscous materials, such as an explosive, out of the structure through an output port or an output port coupled to a nozzle. A transparent materials tube may be provided to facilitate visual monitoring of the material flow. Localized and system wide pressure is controlled by structural design, material application on a structural component or control mechanisms to mitigate or eliminate a possibility of unintended effects from extrusion of the material including explosion due to overly high pressures between components of the extruder system.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

The invention described herein was made in the performance of officialduties by an employee of the Department of the Navy and may bemanufactured, used, licensed by or for the United States Government forany governmental purpose without payment of any royalties thereon.

FIELD OF THE INVENTION

The invention relates to material dispensing and to a method andapparatus for large volume extrusion of viscous materials and especiallyviscous explosive material.

BACKGROUND OF THE INVENTION

Explosives play a large role in many drilling, excavating, mining,oilfields and demolition operations. However, such activities often takeplace far from any developed infrastructure of roads or power utilities.In remote areas there is usually very limited infrastructure to supportsuch activities. Nevertheless, in such situations it is necessary totransport and apply the necessary explosives where needed quickly andwith unimpeded mobility.

A wide variety of explosive materials are available in bulk form on thecommercial and military markets, and these come in all forms includingliquids, gels, slurries, granulated particulate, crystalline powder andcast or pressed solids. One method of employing explosives is to bore ahole or series of holes in the object or material to be moved ordestroyed and insert the explosive into the hole. The explosive can thenbe detonated to achieve the objective. Where multiple boreholes are usedthe timing and power of the explosive charges can be carefullymanipulated to control the shape, area and result of the applied force.This is often done in surface mining operations to remove rockoverburden and in structural demolition to control the rate anddirection of the fall of the structure.

In one example, liquid and slurry explosives, or granulated products areamong the easiest to insert into a borehole, and are effective as longas the borehole is drilled down into non porous or fractured rock.Unfortunately, where holes are drilled horizontally or vertically upand/or into porous and fractured surfaces they cannot contain theexplosive and control of the charge is difficult. Solid explosives,often in stick or shaped form, may be inserted into boreholes in mostany direction or material, but are difficult to insert deeply or intoirregularly shaped openings.

Existing systems require considerable equipment and machinery and areimprecise in terms of the quantity of explosive material inserted intothe hole. What is needed is a more portable, lightweight and safematerial dispenser adapted to manipulate or extrude materials includingexplosive material.

SUMMARY OF THE INVENTION

The present invention provides a portable lightweight, safe, userreloadable and reliable means for extruding or dispensing viscousmaterials into boreholes or any other location. Embodiments of theinvention allow visual observation and control of the application rateand/or volume. One embodiment of the invention generally comprises atrigger valve, supportive chassis, a material tube or enclosure and aportable high-pressure air source (e.g., a SCUBA tank for example). Auser controls the flow of the high-pressure air with the trigger andadjustable regulator and relief valves. The air moves a piston inside amaterial tube and forces explosive material out of the tube/enclosure,through a nozzle and into the borehole or other location desired.

The dispenser according to one embodiment of the present inventionincorporates a transparent polymer (acrylic) material tube that allows auser to see the movement of the material and to start and stop the flowas required. Movement of the material and internal piston is clearlyvisible through the wall of the transparent Users can use a referencetable/aid to associate piston travel, temperature of material to beextruded and material properties with displacement volume and/or travelrequired to effect a specific explosive result

DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same become betterunderstood by reference to the following detailed description when takenin conjunction with the accompanying drawings.

FIG. 1 is a side view of a dispenser with a material tube and end cappartially cut away.

FIG. 2A is detailed partial section of a nozzle cone/tube connection.

FIG. 2B is a schematic view of a dispenser in operation with a nozzleextension tube

FIG. 3A is detailed partial cutaway section of an end cap/tubeconnection.

FIG. 3B is a partial perspective view of an end cap/tube connection.

FIG. 3C is a rear elevation view of the end cap.

FIG. 4 is a perspective view of an embodiment of the dispenser.

Corresponding reference characters indicate corresponding partsthroughout the several views. Although the drawings representembodiments of various features and components according to the presentinvention, the drawings are not necessarily to scale and certainfeatures may be exaggerated in order to better illustrate and explainthe present invention. The exemplification set out herein illustratesembodiments of the invention, and such exemplifications are not to beconstrued as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiment illustrated inthe drawings, which is described below. The embodiment disclosed belowis not intended to be exhaustive or limit the invention to the preciseform disclosed in the following detailed description. Rather, theembodiment is chosen and described so that others skilled in the art mayutilize their teachings. It will be understood that no limitation of thescope of the invention is thereby intended. The invention includes anyalterations and further modifications in the illustrated devices anddescribed methods and further applications of the principles of theinvention which would normally occur to one skilled in the art to whichthe invention relates.

The invention is a method and apparatus for dispensing of viscousmaterials. One embodiment of a dispenser according to the presentinvention incorporates a transparent polymer (e.g., acrylic) tube thatallows a user to see the movement of the material and to start and stopthe flow as required. This results in more accurate and more rapiddispensing of material. An embodiment of the invention is adapted forlarge volume extrusion of explosives designed to operate at the highpressures necessary to extrude high viscosity explosive materials to asufficient depth in an internal area of a structure or area to besubjected to demolition.

FIG. 1 shows a partial cutaway section view of a dispenser system 10with a transparent tube 20 according to one embodiment of the presentinvention. Tube 20 has, in this embodiment, an outside diameter ofapproximately 5 inches and a length of approximately 22 inches, and isformed from a transparent polymer. Clear polymethyl methacrylate (PMMAor acrylic) can be used for manufacture of the tube 20 owing to itsstrength and weight properties as well as its transparency and relativeeconomy of cost and availability. Other compounds such as clearpolystyrene or polycarbonate plastics are similarly suitable butgenerally come at a higher cost. Transparent monomers and othermaterials having the necessary characteristics, notably transparency,may also be suitable.

Tube 20 can be formed or machined with threads 21 along its outsidesurface at outlet end 22, and as well at inlet end 24 for attachment offittings. Specifically, in this embodiment, an aluminum collar adapter26 having internal threads 28 (See FIG. 2A) is threaded over the outsideof tube 20 to facilitate attachment of an extrusion nozzle at outlet end22.

FIG. 2A shows a detailed partial section of a nozzle cone/tubeconnection in accordance with an exemplary embodiment of the invention.The extrusion nozzle comprises a nozzle cone 30 having a flange 36delimiting an annular tube seat 32 for press-fit insertion through thecollar adapter 26 and into the outlet end of the material extrusion tube20. The tapered mating flange 29 of collar adapter 26 contacts thecorresponding tapered flange 36 of the nozzle cone 30 indicating thenozzle cone/tube are fully seated. The annular tube seat 32 is definedby an annular groove 34 for seating an O-ring which may be used to sealthe connection of nozzle cone tube seat 32 and tube 20. A hingedcircular clamp 31 is defined by a flange-receiving groove 33circumscribed about its inner surface, and clamp 31 is fitted over theadjoined tapered flanges 29, 36 of the nozzle cone 30 and collar adapter26, and is tightened thereby compressing the tapered flanges andsecuring nozzle cone 30 to the outlet end of the material extrusion tube20. Circular clamp 31 is necessary to secure nozzle cone 30 at systemoperating pressures within a normal range of from 100-250 psi, and ispreferably strength-rated to withstand a maximum operating pressure thatexceeds the strength rating of the tube 20 itself, for example,approximately 750 psi.

Nozzle cone 30 is formed to taper down from the tube 20 diameter to, inthe present embodiment, an extrusion aperture 38 of approximately 1 inchin diameter over the approximately 6 inches length of the cone. Thediameter of the extrusion aperture 38 and length of the nozzle 30 may bevaried in relation to the bore hole size and explosive materialviscosity. This embodiment of the present invention is adapted todispense material having a viscosity up to 2,000,000 centipoise. Nozzlecone 30 is ideally constructed of machined aluminum although othermaterials having similar strength, weight and machine-abilitycharacteristics may be alternately used. One skilled in the art shouldunderstand that an extension tube 51 (e.g., see FIG. 2B), preferably ofup to four feet in length, may be mated with the nozzle outlet toprovide additional control over explosives or material placement. Tube51 ensures that explosive materials is situated as desired within astructure subjected to demolition prior to detonation rather than in aless effective external or surface placement position.

FIG. 3A shows a detailed partial cutaway section of the end cap/tubeconnection at the inlet end of the material extrusion tube 20 inaccordance with an exemplary embodiment of the invention. A flanged endcap 40 having tube seat 42 and annular groove 44 is inserted into thetube 20 until the tube contacts flange 46 indicating the tube is fullyseated. An O-ring at groove 44 may be used to seal the connectionbetween end cap tube seat 42 and tube 20. Retaining ring 50 having valveaperture 52 (See FIG. 3C) is inserted over end cap 40 such that thethreads on the interior of the retaining ring engage the threads on theoutside of the inlet end of the material extrusion tube 20. Tighteningthe threaded connection between the tube 20 and the retaining ring 50draws the flange 55 of ring 50 up against end cap 40 thereby sealing itin tube 20. Retaining ring 50 is necessary to secure end cap 40 atsystem operating pressures and is preferably rated to at least 750 psi.

Two threaded tapered holes are provided at the back plate of end cap 40.As seen in FIGS. 3A through 3C, an adjustable pressure relief valve 60may be installed in the back plate to control and release excess gaspressure in the extrusion tube. Various adjustable pressure reliefvalves for manual and automatic release can be used. An air filler port62 can be installed at another hole in the back plate. Filler valve 68is connected to filler port 62 and may be rigidly affixed to end cap 40or may be fixed elsewhere and connected to filler port 62 via flexibletubing 64, as depicted in FIG. 4. Filler valve 68 may be operated bypistol grip actuator 63. Filler valve 68 is connected to a high pressuregas source (a SCUBA tank, for example, or a mechanical compressor) byflexible tube 69 via regulator valve 65. Regulator valve 65 may beadjusted to control the maximum pressure admittable into tube 20 byvalve 68 in the full open position. The fluid or gas source, in oneembodiment, is preferably a portable high pressure gas source and morepreferably a portable highly pressurized air source, although alternateembodiments of the present invention may employ any pressurized gas orliquid. Filler valve 68 controls the operational flow of gas into tube20 from the source. Overall flow of gas may be controlled by regulatorvalve 65 and monitored by gauge 66.

Returning to FIG. 1, before the inlet end of tube 20 is sealed by endcap 40 as described above, piston 70 is inserted into the tube 20.Piston 70 in this exemplary embodiment is cylindrical in form andslightly smaller in diameter than the inside diameter of tube 20 so asto be in sealed yet slideable engagement with an interior surface oftube 20. Piston 70 can further be formed with annular grooves 72 at eachend for seating O-rings that improve the quality of the sealedengagement between piston 70 and tube 20. It should be understood thatthe quality of the sealing engagement between piston 70 and tube 20 willvary depending on a series of design parameters including, but notlimited to, the allowable or desired explosive residue level on theinterior surface of the tube, the degradation parameter for cylinderreuse, the explosive detonation characteristics, the operatingenvironment temperature range, and the type of piston used and materialfrom which it is constructed. Piston 70 is preferably fabricated fromacetal polyoxymethylene (available from Dupont™ under the trade nameDelrin® as well as from other suppliers), although other materials maybe chosen based on their strength, weight and friction characteristics.The insertion of piston 70 into tube 20 divides the tube into two areas,a gas expansion area 80 behind the cylinder and between the end cap 40and a material area 82 in front of the piston 70 and between the nozzlecone 30.

One embodiment of the invention can be produced by the following steps:piston or member 70 is inserted into a tube so as to be closer to theinlet end 24 such that a gas expansion area is small, approaching zerovolume, and a material area is consequently large in relation. Amaterial area in the tube is filled with a viscous explosive materialand a nozzle cone is secured to seal an outlet end 22 save for anextrusion aperture 38 through which the material will be extruded duringoperation. A preferably portable high pressure gas source is connectedto regulator valve 65 and the unit is deployed to any locationexplosives are necessary.

In an exemplary operation, as depicted in the embodiment of FIG. 2B,after identification of a hole or recessed area where explosive materialis needed, a nozzle tube extension 51 is inserted into hole or accessarea until it reaches a desired depth or position. A filler valve orcontrol 68 is then opened allowing compressed gas to flow into gasexpansion area 80. Pressure in the gas expansion area quickly increasessuch that the piston 70 is displaced laterally in the tube. Lateraldisplacement of the piston enlarges the gas expansion area 80 andconsequently shrinks the material area 82 forcing some of the viscousexplosive material to be extruded into the bore hole. Depending on theviscosity of the explosive material (which is itself dependent onfactors including ambient temperature), operating pressure of thisembodiment is between 100 and 250 psi.

Extrusion of explosive material will continue in this embodiment as longas an operator maintains the filler valve 68 in the open positionallowing pressurized gas to flow into the gas expansion area. As thevolume of the gas expansion area is increased by the lateraldisplacement of the piston additional compressed gas is necessary tomaintain the operating pressure. Extrusion will cease or reduce in flowupon closing the air filler valve control. Lateral displacement of apiston is clearly visible to an operator through the clear walls of theacrylic material tube so as to allow the operator to monitor the rateand volume of explosive material extruded. An operator can stop orreduce gas flow at any time by releasing or manipulating the fillervalve, and can resume extrusion as desired. Tube 20 may be calibratedwith markings along its longitudinal axis indicating the distance thatpiston 70 has been displaced. A table based on the volume of tube 20 maybe provided to correlate piston travel, material properties, materialtemperature or other factors with a volume of material extruded. In thisexemplary embodiment, an additional manually actuated bleed valve 61(e.g., FIG. 4) is provided to depressurize the system when the operationis complete for disassembly and/or reloading. Field reloading, in oneembodiment, is accomplished by removing nozzle cone 30, returning piston70 to its original position, placing additional material to be dispensedin area 82, and replacing the nozzle cone.

In addition to buildup and sudden discharge of pressure, the design ofone exemplary embodiment of the present invention serves to eliminatethe potential for pinch points to develop at metal on metal contactpoints within the device. Such pinch points potentially trap explosivesdeveloping localized high pressure zones that can cause detonation ofthe material. The long taper of the nozzle cone, the relieved corners ofthe non-metal piston assembly and the use of pliable gasketing orO-rings all serve to reduce the pinch risk and hence the risk ofunintended detonation. For example, care can be taken to ensure that noelement of a material enclosure or structure with explosive in contactthereof presents an orthogonal surface which may come into contact witha piston so as to avoid pinching of explosive material between saidsurface and the piston during operation. An example of avoiding pinchspots can include ensuring the piston face and an interior portion ofthe nozzle facing the piston face do not exert sufficient pressure on anexplosive material between them so as to present an explosives safetyhazard. Other design features such as coating all or part of an interiorof a structure(s) in contact with explosives with silicon or otherfriction reducing coating can also be used to increase safety andoperation of an apparatus in accordance with the invention. Otherfeatures can be included including temperature controls for controllinga temperature of explosives within a structure or part thereof can alsobe used to ensure viscosity of materials to be extruded is within arange desired for use with an embodiment in accordance with theinvention.

It should be understood that the invention may be used with a variety ofmaterials and used beyond lightweight and portable explosive dispensersincluding feeding baby whales Consequently, while this invention hasbeen described as having an exemplary design, the present invention maybe further modified within the spirit and scope of this disclosure. Thisapplication is therefore intended to cover any variations, uses, oradaptations of the invention using its general principles. Further, thisapplication is intended to cover such departures from the presentdisclosure as come within known or customary practice in the art towhich this invention pertains.

1. A dispenser for extruding a viscous material, comprising: a housinghaving a longitudinal axis and defining an enclosure for containing aquantity of a viscous material, said housing having an outlet openingand an inlet opening in communication with said enclosure, said housingfurther constructed of transparent material; a partition in slidable andsealed engagement with an interior surface of said enclosure, saidpartition variably defining a first and second area within saidenclosure wherein said first area is adapted to receive said viscousmaterial between a first side of said partition and said outlet openingand said second area is variably defined between a second side of saidpartition and said inlet opening; a plurality of control mechanisms inselectable communication between a pressurized fluid or gas source andsaid second area; whereby said control mechanisms are adapted toselectively admit pressurized gas or fluid into said second area todisplace said partition along said longitudinal axis toward said outletopening, thereby forcing said viscous material to be extruded from saidfirst area though said outlet opening.
 2. The dispenser of claim 1wherein said plurality of control mechanisms includes a first and secondcontrol mechanism.
 3. The dispenser of claim 2 wherein said firstcontrol mechanism is a proportional flow control valve.
 4. The dispenserof claim 3 wherein said second control mechanism is a pressure reliefvalve whereby the maximum pressure in said enclosure is limited.
 5. Thedispenser of claim 2 further comprising a third control mechanismadapted to further control said gas or fluid in communication with saidsecond area.
 6. The dispenser of claim 5 wherein said third controlmechanism is a pressure regulator valve whereby the maximum pressure ofgas or liquid input into said second area by operation of saidproportional flow valve is selectively controlled.
 7. The dispenser ofclaim 1 wherein no surface contacting said first area is orthogonal tosaid longitudinal axis of said housing whereby localized areas of highpressure within said viscous material due to compression of saidmaterial between said surface and the advancing partition are precludedas the partition is advanced to the fully displaced position.
 8. Thedispenser of claim 7 wherein said enclosure is formed with distancereference markings along said longitudinal axis adapted to indicate adistance said partition has been displaced along said longitudinal axis.9. The dispenser of claim 7 wherein said enclosure is a cylinder. 10.The dispenser of claim 9 wherein said cylinder has a body of transparentmaterial.
 11. The dispenser of claim 9 wherein said outlet opening issealingly engaged to a tapered nozzle.
 12. The dispenser of claim 11wherein said tapered nozzle is removably engaged to facilitate loadingand reloading of said viscous material into said first area.
 13. Thedispenser of claim 7 wherein said partition is a piston or disk.
 14. Thedispenser of claim 13 wherein said piston or disk is comprised of acylinder and at least one O-ring.
 15. The dispenser of claim 13 whereinsaid piston or disk is constructed of electrically nonconductivematerial.
 16. The dispenser of claim 13 wherein said piston or disk isconstructed of material selected to reduce friction between said pistonand said enclosure.
 17. The dispenser of claim 7 wherein said enclosureis adapted to dispense material at between 100 pounds per square inchand 250 pounds per square inch of pressure.
 18. The dispenser of claim 7wherein said enclosure is adapted to extrude viscous material having aviscosity of 13,000 centipoise to 2,000,000 centipoise.
 19. A largevolume viscous explosives extruder, comprising: a housing defining atransparent cylindrical tube for containing a quantity of said viscousexplosive material, said tube having an outlet opening at one end and aninlet opening at the opposite end along a longitudinal axis; a taperednozzle sealingly engaged at the outlet opening; a non-metallic pistonsealingly engaged with the interior surface of said tube and defining afirst area in said tube between said piston and said nozzle in whichviscous explosive material is housed; an end cap sealingly engaged atsaid inlet opening of said tube and defining a second area in said tubebetween said piston and said end cap; at least one inlet aperture insaid end cap; and a variable flow control valve coupled to said inletaperture and adapted to admit pressurized gas, said valve interposedbetween said inlet aperture and a conduit in communication with a highpressure gas source whereby an operator may selectively admitpressurized gas into said second area linearly transposing said pistontoward said nozzle thereby forcing said viscous explosive material to beextruded though said nozzle.
 20. The dispenser of claim 19 wherein nosurface of said housing contacted by said viscous material is orthogonalto said longitudinal axis.
 21. The extruder of claim 20 furthercomprising a pressure relief valve sealingly engaged to an outletaperture of said second area whereby the maximum pressure in saidenclosure is limited.
 22. The extruder of claim 21 further comprising apressure regulator valve interposed between said gas source and saidvariable flow control valve whereby the maximum pressure of gasadmittable to said second area by operation of said variable flowcontrol valve is limited.
 23. The extruder of claim 22 wherein saidvariable flow control valve is trigger actuated.
 24. A method ofdispensing a viscous explosive compound comprising the steps of:providing a transparent enclosure having an outlet opening and an inletopening for containing a quantity of said viscous material; providing apartition slideably inserted into sealed engagement with at least oneinterior surface of said enclosure and defining a first area betweensaid partition and said outlet opening in which said viscous material iscontained, said partition further defining a second area between saidpartition and said inlet opening; providing a plurality of controlmechanisms in communication between a pressurized fluid or gas sourceand said second area, said control mechanisms including a flow controlvalve coupled to an inlet aperture in said second area and adapted toreceive gas from a pressurized gas source; providing a high pressurefluid or gas source coupled to said flow control valve; positioning saidoutlet opening at the point where viscous material is required;selectively allowing fluid or gas to flow from said high pressure gassource to said second area by operation of said valve whereby the fluidor gas pressure in said second area forces said partition to bedisplaced into said first area causing the viscous explosive to beextruded at said outlet opening; visually monitoring the flow of theextruded material; and reducing flow of fluid or gas into said secondarea upon observing that the desired amount of material has beenextruded.
 25. The method of claim 24 further comprising the step ofproviding an extension tube in sealed connection with said outletopening.
 26. The method of claim 25 wherein the step of positioning saidoutlet opening is further comprised of inserting said extension tubeinto a hole.
 27. A method of manufacturing a viscous material extrudercomprising the steps of: providing an enclosure for containing aquantity of said viscous material, said enclosure having an outletopening and an inlet opening; providing a partition slideably insertedinto sealed engagement with at least one interior surface of saidenclosure such that a first area is formed in said enclosure from whichsaid outlet opening is transposed, the balance of said enclosure forminga second area; providing a plurality of pressure control mechanisms insealed engagement with said second area, said control mechanismsincluding a flow control valve adapted to receive fluid or gas from apressurized fluid or gas source.
 28. The method of manufacturing aviscous material extruder of claim 27 further comprising the step ofproviding a pressure relief valve coupled to an aperture into saidsecond area of said enclosure whereby the maximum pressure in saidenclosure is limited.
 29. A method of manufacturing a material extruder,comprising providing a housing having a longitudinal axis and definingan enclosure for containing a quantity of a viscous material, saidhousing having an outlet opening and an inlet opening in communicationwith said enclosure, said housing further constructed of transparentmaterial; providing a partition in slidable and sealed engagement withan interior surface of said enclosure, said partition variably defininga first and second area within said enclosure wherein said first area isadapted to receive said viscous material between a first side of saidpartition and said outlet opening and said second area is variablydefined between a second side of said partition and said inlet opening;providing a plurality of control mechanisms in selectable communicationbetween a pressurized fluid or gas source and said second area, whereinsaid control mechanisms are adapted to selectively admit pressurized gasor fluid into said second area to displace said partition along saidlongitudinal axis toward said outlet opening, thereby forcing saidviscous material to be extruded from said first area though said outletopening.
 30. A method as in claim 29 wherein said plurality of controlmechanisms includes a first and second control mechanism.
 31. A methodas in claim 30 wherein said first control mechanism is a proportionalflow control valve.
 32. A method as in claim 31 wherein said secondcontrol mechanism is a pressure relief valve whereby the maximumpressure in said enclosure is limited.
 33. A method as in claim 32further comprising providing a third control mechanism adapted tofurther control said gas or fluid in communication with said secondarea.
 34. A method as in claim 33 wherein said third control mechanismis a pressure regulator valve whereby a maximum pressure of gas orliquid input into said second area by operation of said proportionalflow valve is selectively controlled.
 35. A method as in claim 29wherein no surface of said housing contacted by said viscous materialand disposed at a pressure interface area is orthogonal to saidlongitudinal axis or are adapted to exert sufficient pressure on saidviscous material as to cause an explosive reaction of said materialbetween said surface of housing and said first side of said partition,wherein said pressure interface area is defined as an area where saidsurface of said housing is substantially adjacent to at least a portionof said first side of said partition when said partition is fullydisplaced within said enclosure towards said outlet opening.
 36. Amethod as in claim 25, wherein said enclosure is formed with distancereference markings along said longitudinal axis adapted to indicate adistance said partition has been displaced along said longitudinal axis.37. A method as in claim 35 wherein said enclosure is a cylinder.
 38. Amethod as in claim 35 further comprising providing a tapered nozzle,wherein said outlet opening is sealingly engaged to said tapered nozzle.39. A method as in claim 38 wherein said tapered nozzle is adapted to beremovably engaged to facilitate loading and reloading of said viscousmaterial into said first area.
 40. A method as in claim 35 wherein saidpartition is a piston or disk.
 41. A method as in claim 40 wherein saidpiston or disk is comprised of a cylinder and at least one O-ring.
 42. Amethod as in claim 40 wherein said piston or disk is constructed ofelectrically nonconductive material.
 43. A method as in claim 40 whereinsaid piston or disk is constructed of material selected to reducefriction between said piston and said enclosure.
 44. A method as inclaim 35 wherein said enclosure is adapted to dispense material atbetween 100 pounds per square inch and 250 pounds per square inch ofpressure.
 45. A method as in claim 40 wherein said enclosure is adaptedto extrude viscous material having a viscosity of 13,000 centipoise to2,000,000 centipoise.
 46. An injector comprising: a housing, saidhousing and an internal surface, said internal surface defining a cavityhaving a longitudinal axis, said cavity being adapted to receive apiston slidingly therewithin where said piston defines a first andsecond variable area disposed on either side of said piston, saidinternal surface including a first surface region, a second surfaceregion, and a transition region between said first and second surfaceregions, said transition region being configured to diverge from acorresponding surface of said piston which is fully displaced towardssaid transition region within said cavity and along a line between saidtransition region and said longitudinal axis so as to form no pinchpoint between said internal surface and said surface of said piston; anda plurality of control mechanisms in selectable communication between apressurized fluid or gas source and said first variable area; wherebysaid control mechanisms are adapted to selectively admit pressurized gasor fluid into said first area to displace said piston along saidlongitudinal axis toward said transition region, thereby forcing saidviscous material to be extruded from said second area though an outletopening in said housing.
 47. An injector as defined in claim 46 whereinsaid transition region comprises an obtuse angle between said firstsurface region and said second surface region.
 48. An injector asdefined in claim 46 wherein said transition region divergessubstantially monotonically from said corresponding surface of saidpiston along said line between said transition region and saidlongitudinal axis.
 49. An injector as defined in claim 46 wherein saidsecond surface region defines a substantially concave surface region.50. An injector as defined in claim 46 wherein said second surfaceregion defines a generally conical surface region.
 51. An injector asdefined in claim 46 wherein said surface of said piston is adapted to bedisposed substantially normal to said longitudinal axis.
 52. An injectoras defined in claim 46 wherein said transition region comprises a linesegment defining an interface between said first surface region and saidsecond surface region.
 53. An injector as defined in claim 46 whereinsaid transition region comprises a curve defining an interface betweensaid first surface region and said second surface region.